Landler, whose reporting on Obama is getting more gushy as the election nears, shone his journalistic flashlight on any slivers of good economic news he could find and suggested they would benefit Obama in the Midwest.

President Obama, betting that the glimmers of a resurgence in the Rust Belt could lift him to victory in the fall, set off Thursday on a two-day bus tour of Ohio and Pennsylvania, promoting himself as a defender of American manufacturing jobs and taking aim at those he said could steal those jobs away.

One of the culprits, Mr. Obama said, is China. Speaking to a happy, if overheated, crowd outside Toledo, he announced that the United States would file a complaint with the World Trade Organization against China for duties imposed on American-made cars and trucks, including the Jeep Wrangler, which is built at an Ohio factory.

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The tour gives Mr. Obama the chance to make an argument that however weak the job market is nationally, the outlook for battleground states like Ohio is brightening. With the release of another potentially poor employment number on Friday, that argument could allow him to weather the ebbs and flows of a fragile economy.

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Still, the Midwest is benefiting from a modest recovery in manufacturing, the lack of a housing bubble that sapped the economy in other parts of the country, and the development of new industries like hydraulic fracturing, or fracking. In a recent statewide survey by Quinnipiac University, Mr. Obama was leading Mr. Romney in Ohio by 47 percent to 38 percent -- his largest lead, where earlier polls showed a close race.

Taking a tough line toward China on trade issues is a tried-and-true strategy during election years. The administration said this was the seventh such action it has taken against China -- including its 2009 move against China for dumping tires in the American market -- a pace that is double that of the Bush administration.

In his first foray outside Washington since the Supreme Court upheld his health care law last week, Mr. Obama also offered a robust defense of the law, saying that Americans did not want to refight the battles of two years ago.

“I’ll work with anybody who wants to work with me to continue to improve our health care system and our health care laws,” he said to cheers. “But the law I passed is here to stay. It is going to make the vast majority of Americans more secure.”

After his speech here, Mr. Obama consoled a woman, Stephanie Miller, who told him that her sister died of cancer four years ago. The sister, Ms. Miller said later in a telephone interview, had not been able to afford health insurance, having been told that she earned too much to qualify for Medicaid.